Halo-substituted benzospiro cyclopropane carboxylates as insecticides and ixodicides

ABSTRACT

The invention is novel halo-substituted benzospiro cyclopropane carboxylates useful for the control of insect pests of agriculturally important crops, and useful as insecticidal and acaricidal agents for the treatment of livestock and domestic animals.

The invention is novel insecticidal-acaricidal pyrethroids of formula:##STR1## wherein R₁ is hydrogen or cyano, and the optical and geometricisomers thereof.

It is recognized, of course, that these isomers will vary somewhat inthe degree of insecticidal and acaricidal activity which they exhibittowards a given pest; however, they are useful as insecticidal and/oracaricidal agents.

The invention also relates to a method for the control of insect pestsof agronomic crops and of ectoparasites, especially ixodide ticks, oflivestock and domestic animals.

Conveniently, the compounds of formula (I) may be prepared by thefollowing reaction sequence: ##STR2## wherein R₁ is as hereinabovedefined; R₂ is C₁ -C₃ alkyl; and X is halogen, preferably chlorine.

In practice, a spirocyclopropanecarboxylic acid ester of formula (II) isreacted with a halogenating agent such as iodobenzene dichloride in thepresence of an inert solvent such as chloroform, methylene chloride,dichloroethane and the like at a temperature range of from 20° C. to 30°C. for a period of time sufficient to essentially complete the reactionand obtain the corresponding dihalo derivative (III). This compound isthen dehydrohalogenated under anhydrous conditions with an alkali metalalkoxide, such as potassium-t-butoxide in the presence of a solvent suchas t-butanol to afford the ester (IV) of the desiredmonochloro-spirocyclopropanecarboxylic acid. The ester (IV) ishydrolized with a base such as potassium hydroxide in a dilute alcoholto yield the acid (V). This acid is then converted to the acid halide,preferably chloride, with thionyl halide, preferably thionyl chloride inthe presence of an inert solvent such as toluene; the acid halide isisolated if so desired, and is then reacted with a benzyl alcohol offormula (VII) in the presence of an acid acceptor such as pyridine andan inert solvent, such as ether to yield the desired insecticide offormula (I).

We find that the compounds represented by formula (I) above are highlyeffective contact and stomach poisons for a variety of insect pests ofcrops, particularly Dipterous, Lepidopterous, Coleopterous andHomopterous insects. These compounds are also effective for the controlof ectoparasites, especially ixodide ticks, of livestock and domesticanimals such as cattle, sheep, horses, dogs, cats and the like.

For the control of insects which attack agricultural crops, thecompounds of this invention may be applied to the foliage of the crops,the insect's habitat and/or the insect's food supply in the form of adilute liquid spray; the compounds may also be applied as a dust,wettable powder, an aerosol or the like.

Dilute, liquid sprays may conveniently be prepared from emulsifiableconcentrates. A typical emulsifiable concentrate may comprise about 24%by weight of toxicant; 4% by weight of a surfactant; 23% by weight of asolvent such as cyclohexanone; and about 45% by weight of a petroleumsolvent having a minimum aromatic content of about 93 volume %.

The compounds of the invention may also be used as systemicinsecticidal-acaricidal agents in the treatment of animals, and as suchmay be administered to the animals orally or parenterally. When givenorally, the active compounds may be formulated as boluses, tablets,capsules or oral drenches; or may be incorporated in an animal feedstuffsuch as a nutritionally balanced diet containing 0.01% to 3.0% andpreferably 0.01% to 1.5% by weight of feed of the active compound.

Systemic insecticidal-acaricidal agents may also be introduced into thebody of the animal by subcutaneous, intramuscular or intraperitonealinjection such that it may be distributed through the animal's body bythe action of the animal's circulatory system. In practice, the toxicantmay be dissolved or dispersed in a pharmaceutically acceptable carrier,such as water, propylene glycol, vegetable oil, glycerol formal, or thelike, for administration.

This invention is further demonstrated by the non-limiting examplesprovided below.

EXAMPLE 1 Preparation of3'-chloro-3,3-dimethyl-spiro[cyclopropane-1,1'-indene]-2-carboxylicacid, α-cyano-m-phenoxybenzyl ester.

Thionyl chloride (2.0 ml) is added dropwise to a suspension of3'-chloro-3,3-dimethyl-spiro[cyclopropane-1,1'-indene]-2-carboxylic acid(1.4g; 0.0056 mole) in dry toluene (20 ml) at room temperature. Thereaction mixture is warmed briefly to 40° C. then is allowed to stir atroom temperature overnight. A dark colored solution forms. The solventand excess thionyl chloride are then removed in vacuo to afford 1.35 gof acid chloride, a red-brown oil. This acid chloride is dissolved inbenzene (20 ml), and added to a solution of α-cyano-m-phenoxybenzylalcohol (1.25 g; 0.005 mole) and pyridine (0.4 g; 0.0051 mole) in etherat 0 to 10° C. The reaction mixture is then allowed to warm up to roomtemperature and is stirred overnight. The crude reaction mixture ischromatographed on a dry column (silica gel; 50:50 methylenechloride:hexane), the fractions are combined and evaporated to afford0.7 g of title product. Elemental Analysis: Calc. C 73.76%; H 4.86%; Cl7.77%; N 3.07%. Found. C 74,03%; H 4.82%; Cl 10.51%; N 2.81%.

EXAMPLE 2 Preparation of3'-chloro-3,3-dimethyl-spiro[cyclopropane-1,1'-indene]-2-carboxylicacid, m-phenoxybenzyl ester.

Pyridine (1.68 g) and thionyl chloride (2.5 g) are added to a mixture of3'-chloro-3,3-dimethyl-spiro[cyclopropane-1,1'-indene]-2-carboxylic acid(5.0 g; 0.02 mole) and ether (50 ml). After two hours at roomtemperature, pyridine (1.68 g) and m-phenoxybenzyl alcohol (4.0 g) areadded and the reaction mixture stirred at room temperature overnight.The reaction mixture is then washed with water, the ether fraction driedover magnesium sulfate and evaporated to dryness. The residue ispurified on a dry column (silica gel; 20% methylene chloride:hexane) toafford 3.0 g of title compound, a yellow-orange liquid. The sample is90-95% pure by NMR, and shows an ester carbonyl stretch at 1730 cm⁻¹ inIR.

EXAMPLE 3 Preparation of3'-chloro-3,3-dimethyl-spiro[cyclopropane-1,1'-indene]-2-carboxylicacid.

A solution of3'-chloro-3,3-dimethyl-spiro[cyclopropane-1,1'-indene]-2-carboxylic acidethyl ester (2.0 g; 0.007 mole) in ethanol (10 ml) is added to a mixtureof 50% aqueous potassium hydroxide (1.2 ml) and water (1.2 ml), and themixture is heated at reflux for 11/2 hours, then cooled down, dilutedwith water and extracted with ether. The aqueous phase is then made acidwith concentrated hydrochloric acid and extracted with ether. Theethereal extract is washed with water, saturated salt solution, driedover magnesium sulfate and is stripped to afford 1.5 g of title product,a read-brown semisolid.

EXAMPLE 4 Preparation of3'-chloro-3,3-dimethyl-spiro[cyclopropane-1,1'-indene]-2-carboxylicacid-, ethyl ester.

A solution of2',3'-dichloro-3,3-dimethyl-spiro[cyclopropane-1,1'-indene]-2-carboxylicacid-, ethyl ester (19 g as is, containing iodobenzene) in t-butanol (50ml) is added to a 0.1 M solution of potassium-t-butoxide in t-butanol(450 ml; 0.045 mole) and the mixture allowed to stir overnight at roomtemperature. The reaction mixture is then poured into water, extractedwith ether, the ether extracts dried over magsium sulfate and evaporatedto dryness to afford 11.1 g of a black oil. This oil is purified bychromatography (silica gel; eluent: 1:1 mixture of methylenechloride:hexane), to afford 2 g of title product, a yellow oil.

EXAMPLE 5 Preparation of2',3'-dichloro-3,3-dimethyl-spiro[cyclopropane-1,1'-indene]-2-carboxylicacid-, ethyl ester.

To a stirred solution of3,3-dimethyl-spiro[cyclopropane-1,1'-indene]-2-carboxylic acid ethylester (7.3 g; 0.03 mole) in chloroform (100 ml) is added iodobenzenedichloride (8.3 g; 0.03 mole) in small increments. Incomplete solutionoccurs. The reaction mixture is stirred overnight at room temperature,after which time a clear solution forms. The solution is stripped invacuo at 50°-60° C. to leave 15.4 g of a residual oil comprising amixture of the title product and iodobenzene as indicated by NMR.

EXAMPLE 6 Preparation of iodobenzene dichloride.

Chlorine gas is bubbled through a solution of iodobenzene (20.4 g; 0.1mole) in chloroform (100 ml) while the temperature of the reactionmixture is maintained at -5° C. In about 10 minutes a yellow solidprecipitates and is removed by filtration. The filtrate is then furthertreated with chlorine gas until the formation of yellow solid ceases.The solid fractions are combined and air dried to afford 25.9 g (94.2%)of title product.

EXAMPLE 7 Evaluation of the test compounds for the control of Ixodidae.

The efficacy of the compounds of the invention for control of ticks isdemonstrated in the following tests wherein engorged adult femaleBoophilus microplus, multiple resistant strain, ticks which have droppedfrom cattle are collected and used for testing.

The compound to be tested is dissolved in a 35% acetone/65% watermixture in amounts sufficient to provide the concentrations indicated inTable I below. Ten ticks per treatment are used and they are immersed inthe test solution for three to five minutes, then removed and held inincubators for two to three weeks at 28° C. Counts of ticks laying eggsare then made and recorded. Eggs which were laid are placed incontainers and kept for one month to observe hatching and to determinechemosterilant effect. Results of these tests are given in Table Ibelow.

Percent reduction in viable egg masses is believed to be indicative ofone or more of the following mechanisms:

1. Killing of the tick.

2. Suppression of fecundity.

3. Chemosterilant effect.

                                      TABLE I                                     __________________________________________________________________________    Evaluation of the Test Compounds for the Control of Ixodidae                                                         Percent                                                                       reduction                                                             Concentration                                                                         in viable                              Compound                       in ppm  egg masses                             __________________________________________________________________________     ##STR3##                      125     98                                      ##STR4##                      125  62 91.9 83.9 72.7  0                      __________________________________________________________________________

EXAMPLE 8 Evaluation of the efficacy of the compounds of the inventionfor the control of Boophilus microplus larvae.

Effective control of acarina larvae is demonstrated in the followingtests with larvae of Boophilus microplus, a one-host tick which canremain on a single host through its three life stages, i.e. larva, nymphand adult. In these tests a 10% acetone/90% water mixture contains thetest compound at the concentrations indicated in Table II below. Twentylarvae are enclosed in a pipet sealed at one end with a gauze material,and a solution, containing the test compound at the concentrationsgiven, is then drawn through the pipet with a vacuum hose simulating aspray system. The ticks are then held for 48 hours at room temperature,and percent mortality rates are then determined. The results obtainedwith the various compounds are tabulated in Table II below.

                                      TABLE II                                    __________________________________________________________________________    Efficacy of the compounds of the invention for the control of                 Boophilus microplus larvae.                                                                                          Percent                                                                       Mortality of                                                          Concentration                                                                         Boophilus                                 Compound                    in ppm  microplus                              __________________________________________________________________________     ##STR5##                      0.78 0.19 0.05 0.012                                                                  80-100 80 (O)*  0  0                    ##STR6##                      100     100                                    __________________________________________________________________________     *Two replicates, one 80%, the other 0% control.                          

EXAMPLE 9 Insecticide testing procedures. Malaria Mosquito (Anophelesquadrimaculatus say) egg and larvae test.

One ml of a 300 ppm solution is pipetted into a 400 ml beaker containing250 ml of deionized water and stirred with the pipette, giving aconcentration of 1.2 ppm. A wax paper ring 0.6 cm wide to fit inside thebeaker is floated on the surface of the test solution to keep the eggsfrom floating up the meniscus curve and drying out on the side of theglass. A spoon made of screen in used to scoop up and transfer about 100eggs (0-24 hours old) into the test beaker. After two days at 26.7° C.observations of hatching are made. This includes kill of eggs orinhibition of hatch, kill of newly hatched larvae, or delayed hatch.Additional observations are made after another day for the same effects.

Tobacco Budworm [Heliothis virescens (Fabricius)].

A cotton plant with 2 true leaves expanded is dipped for 3 seconds withagitation in a 300 ppm solution. A 1.25 to 2 cm square of cheeseclothwith about 50 to 100 budworm eggs 0-24 hours old is also dipped in thetest solution and placed on one leaf to dry. The leaf with the treatedbudworm eggs is removed from the plant and placed in a 236.6 ml (8-oz.)Dixie cup with a wet 5 cm piece of dental wick and covered with a lid.The other leaf is placed in a similar cup with a wick and a piece ofcheesecloth infested with 50-100 newly hatched larvae is added beforecovering the cup with a lid. After 3 days at 26.7° C., observation ofegg hatch are made as well as kill of newly hatched larvae, anyinhibition of feeding, or interference of any sort with normaldevelopment.

Phosphate-Resistant Strain of Two-Spotted Spider Mite [Tetranychusurticae (Koch)].

Sieva lima bean plants, with primary leaves 7.6 to 10 cm long, areinfested with about 100 adult mites per leaf 4 hours before use in thistest, in order to allow egg-laying before treatment. The infested plantsare dipped for 3 seconds with agitation into a 300 ppm solution, and theplants set in the hood to dry. After 2 days at 26.7° C., the adult mitemortality is estimated on one leaf under a 10X stereoscopic microscope.The other leaf is left on the plant an additional 5 days and thenexamined at 10X power to estimate the kill of eggs and of newly-hatchednymphs, giving a measure of ovicidal and residual action, respectively.

Southern Armyworm [Spodoptera eridania (Cramer)].

A Sieva lima bean plant with just the primary leaves expanded to 7.6 to10 cm is dipped for 3 seconds with agitation in a 1000 ppm solution andset in a hood to dry. Following this, one leaf is placed in a 10 cmpetri dish which has a moist filter paper in the bottom and 10third-instar armyworm larvae about 1 cm long. The dish is covered andheld at 26.7° C. After 2 days mortality counts and estimates of theamount of feeding are made. Compounds showing partial kill and/orinhibition of feeding are held for an extra day for furtherobservations.

All compounds showing activity as defined above are retested, using thesecond leaf on the bean plant, after an interval of 7 days from originaltreatment, as an assay of residual activity.

Mexican Bean Beetle (Epilachna varivestis Mulsant)

Sieva lima bean plants (2 per pot) with primary leaves 7.6 to 10 cmlong, are dipped in a 300 ppm solution and set in a hood to dry. Oneleaf is removed from the plant and placed in a 10 cm petri dishcontaining a moist filter paper on the bottom and 10 last-instar larvae(13 days from hatching).

The day after treatment, another leaf is removed from the plant and fedto the larvae after removing the remains of the original leaf. Two daysafter treatment, the third leaf is fed to the larvae, this usually beingthe last needed. The fourth leaf is used on the third day aftertreatment if the larvae have not finished feeding. The test is now setaside and held until adults have emerged, usually about 9 days aftertreatment began. After emergence is complete, each dish is examined fordead larvae, pupae or adults; deformed pupae or adults; larval-pupalintermediates or pupal-adult intermediates; or any other interferencewith normal molting, transformation and emergence of pupae or adults.

Western Potato Leaf Hopper (Empoasca abrupta DeLong)

A lima bean plant with the primary leaf expanded to 7.6 to 10 cm isdipped into a 100 ppm solution and set in a hood to dry. A 2.5 cm pieceof the tip of 1 leaf is cut off and placed in a 10 cm petri dish with amoist filter paper in the bottom. (In practice, this is usually cut offthe tip of a plant from the Mexican bean beetle tests using a bean leafdipped in the needed solution). From 3 to 10 second-instar nymphs aretapped from the culture plants into the test dish and rapidly covered.Mortality counts are made after two days at 26.7° C.

Malaria Mosquito (Anopheles quadrimaculatus Say) Adult Test.

Ten ppm solutions are poured into wide-mouth 46.2 ml jars eachcontaining a microscope slide. The slides are removed from the testsolution with forceps and laid horizontally to dry on a wide-mouth 118.4ml bottle. When dry, they are placed in the same 118.4 ml bottle and ten4 to 5-day old mosquitoes of mixed sexes are added to each bottle. Apiece of cotton gauze held on by an elastic band serves as a lid and awad of cotton soaked in 10% honey solution serves as food. Mortalitycounts are made after 1 day at 26.7° C.

Bean Aphid (Aphid fabae Scopoli).

Five cm fiber pots, each containing a nasturtium plant 5 cm high andinfested with 100 to 500 aphids 2 days earlier are placed on a 4 rpmturntable and sprayed with a 100 ppm solution for 2 revolutions with aNo. 154 DeVilbiss Atomizer at 1.4 kg/cm² air pressure. The spray tip isheld about 15 cm from the plants and the spray directed so as to givecomplete coverage of the aphids and the plants. The sprayed plants arelaid on their sides on white enamel trays. Mortality estimates are madeafter 1 day at 26.7° C.

Tobacco Budworm [Heliothis virescens (Fabricius)]. Third instar.

Three cotton plants with just expanded cotyledons are dipped in a 1000ppm solution, and placed in a hood to dry. When dry, each cotyledon iscut in half and 10 are each placed in a 29.6 ml plastic medicine cupcontaining a 1.25 cm dental wick saturated with water, and onethird-instar budworm larva is added. The cup is capped and held for 3days at 26.7° C., after which mortality counts are made.

Cabbage Looper. [Trichoplusia ni (Hubner)].

A primary leaf of a cotton plant is dipped in the test solution andagitated for 3 seconds. It is then set in a hood to dry. Following this,the leaf is placed in a 10 cm petri dish containing a moist filter paperat the bottom and 10 third-instar loopers. The dish is covered and heldat 26.7° C. After 2 days, mortality counts and estimates of feedingdamage are recorded. Those materials showing partial kill and/orinhibition of feeding are held for another day for further observations.

The rating system employed in these tests is as follows:

Rating System

0=0-40% killed or affected

1=reduced feeding (trace to light damage)

2=some deformed insects (40-80%)

3=mostly deformed insects (85-100%)

4=not an index number at present

5=51-60% mortality

6=61-70% mortality

7=71-85% mortality

8=86-95% mortality

9=100% mortality

The absence of a number indicates that no test has been run at thatparticular dosage.

Compounds rated active (8 or 9) are further tested at reducedconcentrations in 50% acetone:50% water.

Data obtained are reported in Table III below.

                                      TABLE III                                   __________________________________________________________________________    Evaluation of the Insecticidal Activity of the Compounds of the               Invention.                                                                                                   Mosquito Larvae                                                                        Tobacco Budworm                                                      ppm      Eggs - ppm                                                                          Larvae - ppm                       Structure                   1.2                                                                              0.4                                                                              0.04                                                                             300                                                                              100                                                                              10                                                                              300                                                                              100                                                                              10                      __________________________________________________________________________     ##STR7##                      9  9  9  0       9  9  9                        ##STR8##                      9  9  9  0       9  9  9                       __________________________________________________________________________

                                      TABLE IIIb                                  __________________________________________________________________________    Evaluation of the Insecticidal Activity of the Compounds of the               Invention.                                                                                                   Phosphate Resistant    Mexican Bean                                           Mites     Southern Armyworms                                                                         Beetles                                                ppm       ppm          ppm                        Structure                   300 100                                                                              10 1000                                                                             100                                                                              10 7-days                                                                            300                                                                              100                                                                              10                __________________________________________________________________________     ##STR9##                      8   5  0  9  9  7  0   9  9  9                  ##STR10##                     8   0     9  9  0      9                       __________________________________________________________________________

                                      TABLE IIIc                                  __________________________________________________________________________    Evaluation of the Insecticidal Activity of the Compounds of the               Invention.                                                                                                                       Tobacco                                                          Mosquito,    Budworm                                                                             Cabbage                                             Leaf Hopper                                                                          Adult Bean Aphids                                                                          3rd   Looper                                              ppm    ppm   ppm    Instar-ppm                                                                          ppm                     Structure                   100 10 10 1  100                                                                              10                                                                              1 1000                                                                             100                                                                              1000                                                                             100               __________________________________________________________________________     ##STR11##                     9   9  9  7 6 9                                                                            9  9 9 5  0  9  9                  ##STR12##                     9   9  0     9  9 0 9  5  9  9                 __________________________________________________________________________

I claim:
 1. A method for preparing compounds of the formula: ##STR13##wherein R₁ is hydrogen or cyano which comprises reacting aspirocyclopropanecarboxylic acid ester of the formula ##STR14## whereinR₂ is C₁ -C₃ alkyl with a halogenating agent in the presence of an inertsolvent at a temperature in the range of from 20° C. to 30° C. for aperiod of time to essentially complete the reaction and obtain thedihalo derivative of the formula ##STR15## dehydrohalogenating thedihalo derivative III under anhydrous conditions with an alkali metalalkoxide in the presence of a solvent to produce the ester ##STR16##hydrolizing the ester IV with a base in a dilute alcohol to yield theacid ##STR17## converting the acid V to the acid halide ##STR18##wherein X is halogen by reacting acid V with a thionyl halide in thepresence of an inert solventisolating the acid halide VI and thenreacting the acid halide VI with a benzyl alcohol ##STR19## in thepresence of an acid acceptor and an inert solvent to yield the compoundof formula I.